1. Field of the Invention
This invention relates to a speaker gasket and its manufacturing method, and a speaker device, and is suitably applied to a cone speaker, for example.
2. Description of the Related Art
There are some cone speakers constructed as shown in FIG. 1.
Such a cone speaker 1 has a conic cone vibratory plate 2 with its center opened. The outer circumference of the cone vibratory plate 2 is fixed to a frame 4 via an edge 3, and the inner circumference which is the central part of the cone vibratory plate 2 is attached to a damper 5 fixed in the frame 4, thereby the cone vibratory plate 2 can be kept so as to vibrate only forwards (arrow a) and backwards without rolling.
In addition, on the outer circumference of the edge 3, a annular gasket 6 made of rubber or the like is fixed, so that the gasket 6 acts as a buffer when this cone speaker 1 is attached to a speaker box or an internal panel of a vehicle. This can previously and effectively prevent unwanted vibration and generation of noise.
Further, at the inner circumference of the cone vibratory plate 2, a cylindrical voice coil bobbin 8 having wounded thereon a voice coil 7 comprising a lead line is fixed together with the damper 5. In front of the opening 2A at the center of the cone vibratory plate 2, a hemisphere head cap 9 is attached so as to cover the opening 2A, with the result that the head cap 9 can previously prevent deformation of the cone vibratory plate 2 in the diameter direction and also prevent dusts from entering the opening 2A of the cone vibratory plate 2.
On the other hand, on the bottom of the frame 4, a magnetic circuit 10 for vibrating the cone vibratory plate 2 forwards and backwards is fixed. This magnetic circuit 10 has a disk yoke 11 provided with a column pole piece 11A at the center of the top, and a toric magnet 12 is fixed so as to surround the outer circumference of the yoke 11 and a toric plate 13 is laminated and fixed on the magnet 12.
When the magnetic circuit 10 is attached to the frame 4 so that the top of the plate 13 is fixed to the bottom of the frame 5, the voice coil bobbin 8 having the voice coil 7 wounded thereon is kept in a contactless manner in a magnetic gap g formed between the pole piece 11A and the plate 13.
Thus in the cone speaker 1, when electromagnetic force is applied to the voice coil 7 according to applied current based on an audio signal externally supplied, the voice coil 7 and the magnet 12 attract and repel each other, thereby generating a sound wave according to the audio signal by vibrating the cone vibratory plate 2 forwards and backwards.
For a manufacturing method of a gasket 6 used in such cone speaker 1, please refer to Japanese Patent Laid-Open No. 1-256499.
By the way, gaskets 6 used in such a cone speaker 1 are normally produced by cutting a sheet material 21 made of, for example, rubber, having a double stick sheet 20 stuck on its one surface, into rings.
In such the conventional manufacturing method, however, since the sheet material 21 is cut so that ring gaskets 6 have curvature, a ratio of unused parts (wasteful part) to parts which are actually used as the gaskets 6 in the sheet material 21 is large and the wasteful parts are difficult to be recycled and just have to be discarded. That is, the sheet material 21 can not be used effectively.
As one technique to solve such problems, the aforementioned Japanese Patent Laid-Open No. 1-256299 proposes such a technique as to cut a sheet material 21 into a flat deformed ring which is like a pressed gasket, and deform this ring to attach to the frame 4 of a cone speaker 1.
In this technique, since the sheet material 21 is cut into flat deformed rings as the gaskets 6, more number of gaskets 6 can be obtained from the sheet material 21, resulting in reducing wasteful parts of the sheet material 21, as compared with the conventional technique.
This technique, however, cannot cut the sheet material into gaskets 6 without wasting parts because the gaskets 6 made from the sheet material 21 are still flat deformed rings and therefore are made with curvature. As a result, this technique is not sufficient in view of effective use of the sheet material 21.
Further, continuous discarding of wasteful material does not match the current general atmosphere considering global environment, and further the wasteful material should be further reduced.